1. Field of the Invention
This invention relates to animal litter and to the production thereof. More particularly it relates to litter which is readily amenable to the removal of odorous animal waste products after use. It particularly relates, without limitation, to cat litter.
2. Brief Description of Related Art
Animal litter and the deodorising of animal litter which has been contaminated by animal waste products has been widely described in the literature. It is common practice to include additives in the litter during manufacture in order to mask or eliminate odours the additive possibly being a perfume or a substance capable of chemically altering the substance or substances responsible for the odour such as a reactive substance such as a suitable acid. Some expedients may be expensive to implement due to the cost of the additives and may often be only partially effective.
It has been realised that a property of certain natural earths which may be used as litter, namely a tendency to "clump", may be utilised to control litter odour. Clumping is a tendency, marked in certain earths and less marked or absent in others, for the earth particles to adhere firmly to each other when wet to form a mass having sufficient physical integrity to enable it to be removed from the remainder of the particles without undue crumbling or loss of peripheral material. The liquid with which the litter has been wet is entrained in the clump and is removed with it. Where the earth has good clumping properties substantially all of the liquid may be retained in the clump and the portion of the earth which remains after the removal of the clump may be completely dry. This property provides a means for removing urine from used litter which, in conjunction with the physical removal of feces, results in a residue of uncontaminated litter, free of undesired odours, which may be replenished with fresh litter. This represents an economical use of litter in comparison with the complete replenishment of the litter.
The present invention relates to the improvement of clumping properties in those earths which naturally show only poor or medium clumping properties. In selecting earths for use according to the invention the degree of clumping of any particular earth may be judged by reference to the results of the clumping test described hereafter. However, while the invention gives its greatest benefit when used in relation to poorly clumping earths, the invention is not limited to such and may be used in relation to any earths suitable for litter use. The earth may for example be a montmorillonite or other smectite, suitably in the alkaline earth metal form, an attapulgite, a palygorskite or a sepiolite.
U.S. Pat. No. 5,014,650 relates to litter comprising a porous, inert solid substrate, such as a clay, containing a cellulosic ether in an amount sufficient to agglomerate the animal urine deposited on the litter to form a gelled agglomerate having sufficient mechanical integrity to be conveyed from the litter box as a discrete entity. Additional polymers disclosed to be useful in the litter include polyvinyl alcohol, xanthan gum, gum acacia and various water-soluble polysaccharides although these, apart from the cellulose ethers, are neither preferred nor exemplified.
U.S. Pat. No. 4,676,196 describes an absorbent non-clay material comprising a mix of particulate materials which are caused to agglomerate to form non-compacted particles of a required size by tumbling in the presence of a moistened binder comprising starches, gums such as guar gum or glues. No materials known to have clumping effect are included in the absorbent material and the binder is included merely as an agglomerating agent.